Effect of therapeutic suggestions during general anaesthesia on postoperative pain and opioid use: multicentre randomised controlled trial

Abstract

Objective: To investigate the effect of therapeutic suggestions played to patients through earphones during surgery on postoperative pain and opioid use.

Design: Blinded randomised controlled study.

Setting: Five tertiary care hospitals in Germany.

Participants: 385 of 400 patients consecutively recruited from January to December 2018 who were to undergo surgery for 1-3 hours under general anaesthesia. In the per protocol analysis 191 patients were included in the intervention group and 194 patients in the control group.

Intervention: The intervention comprised an audiotape of background music and positive suggestions based on hypnotherapeutic principles, which was played repeatedly for 20 minutes followed by 10 minutes of silence to patients through earphones during general anaesthesia. Patients in the control group were assigned to a blank tape.

Main outcome measures: The main outcome was dose of opioid administered by patient controlled analgesia or nurse controlled analgesia within the first postoperative 24 hours, based on regular evaluation of pain intensity on a numerical rating scale (range 0-10, with higher scores representing more severe pain).

Results: Compared with the control group, the intervention group required a significantly (P=0.002) lower opioid dose within 24 hours after surgery, with a median of 4.0 mg (interquartile range 0-8) morphine equivalents versus 5.3 (2-12), and an effect size (Cohen's d) of 0.36 (95% confidence interval 0.16 to 0.56). The number of patients who needed opioids postoperatively was significantly (P=0.001) reduced in the intervention group: 121 of 191 (63%, 95% confidence interval 45% to 70%) patients in the intervention group versus 155 of 194 (80%, 74% to 85%) in the control group. The number needed to treat to avoid postoperative opioids was 6. Pain scores were consistently and significantly lower in the intervention group within 24 hours after surgery, with an average reduction of 25%. No adverse events were reported.

Conclusions: Therapeutic suggestions played through earphones during general anaesthesia could provide a safe, feasible, inexpensive, and non-drug technique to reduce postoperative pain and opioid use, with the potential for more general use. Based on the finding of intraoperative perception by a considerable number of patients, surgeons and anaesthetists should be careful about background noise and conversations during surgery.

Trial registration: German Clinical Trial Register DRKS00013800.

Fig 1

Flow of patients through the study. No postoperative data were collected for dropouts and they were excluded from analysis before unblinding of the study. ICU=intensive care unit

Fig 2

Postoperative dose of opioids within 24 hours after surgery. Data are calculated by bootstrapping owing to non-normally distributed outcome variables. Doses are in morphine milligram equivalents (MME) to account for different types of opioids (intravenous morphine=1.0, piritramide=0.7, tilidine=0.2, oxycodone=0.8) used in one centre

Fig 3

Course of preoperative and postoperative pain levels. Data are calculated from mean values by bootstrapping owing to non-normally distributed outcome variable. Dashed line represents the numerical rating scale threshold of 3 for pain treatment. Whiskers represent 95% confidence intervals.